The invention relates to a method for producing a battery, comprising the steps of:
preparing a first electrode by providing a substrate and depositing at least one semiconductor layer on the substrate;
generating a particular porosity across a particular region of the semiconductor layer;
arranging the first electrode together with a second electrode and an electrolyte within a housing;
contacting the two electrodes and connecting with external terminals accessible from outside the housing.
The invention further relates to a battery with two electrodes which are connected with each other by means of an electrolyte for allowing a current flow between the two electrodes.
Such a method and such a battery are known from U.S. 2010/02211606 A1.
Accordingly, at the beginning an electrically conductive substrate is provided and a semiconductor layer is deposited thereon and anodized, whereby pores are formed in the semiconductor layer. The first electrode generated in this way comprises an increased surface it is combined with a second electrode and with an electrolyte, for providing a battery. The substrate may be an endless foil which can be rolled to a cylindrical shape. By the anodizing the surface of the semiconductor layer is increased to generate a controlled, porous structure.
In the development of rechargeable lithium-ion-batteries up to now one has relied on carbon material with large surface as an anode material, such as Mesocarbon Microbeads (MCMB) to obtain a power density as high as possible.
However, the power density of carbon-based material is relatively limited.
Due to these reasons, different anode materials based on silicon have been developed lately. Differing from a storing of lithium between individual carbon layers, silicon forms an alloy with lithium. Negative electrodes based on silicon are of interest due to their high theoretical specific capacity which is considerably higher than the one of carbon.
However, a particular problem with the utilization of silicon as an electrode material rests in the considerable volume enlargement which is due to the intake of atoms which may lead to stresses, fracture generation and in the very end to a breakdown of the electrode. Due to this reason, according to U.S. 2010/0221606 A1 mentioned at the outset it was tried to prepare the silicon electrode with a controlled porosity for limiting the volume increase during the intake of lithium. However, the anodizing step used in this regard is not sufficient to counteract a swelling of the silicon layer sufficiently.
From U.S. 2012/0231326 A1 a further method for producing a rechargeable battery with an anode made of a porous silicon layer is known. Herein the porous silicon layer is generated by electrochemical etching and a subsequent coating with a passivation layer. For obtaining the porous silicon layer a particular etching treatment is performed.
However, the production method is complicated, and still the potential for limiting the volume increase during the intake of lithium ions is limited. Also in a lithium-ion-battery known from U.S. 2013/0078508 A1 an anode with porous silicon is utilized. The anode preferably is in the form of nano-fibers, a foil or a powder with porous silicon with pore diameters in the range of 2 nm to 100 nm and an average wall thickness in the range of 1 nm to 100 nm. For preparing the porous silicon layer, an etching method is used.
Also herein the production method is complex and still the capacity of the silicon layer for the intake of ions is relatively limited.
Apart from that, as an alternative to lithium-ion-secondary batteries also non-rechargeable metal/air batteries have been developed. Since a considerable time it has been worked on the development of silicon/air batteries that have a high theoretical energy density of 8470 Wh/kg.
Also herein the volume increase of the silicon layer during the intake of ions is one of the central problems.